LT3045 datasheet(37/45 Pages) AD

37 / 45 page

Data Sheet

LT83201

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Rev. A 37 of 45

Thermal Considerations

For higher ambient temperatures, care should be taken in the layout of the PCB to ensure good heat sinking of the

LT83201. The exposed pad on the bottom of the package should be soldered to a ground plane. This ground should

be connected to large copper layers below with thermal vias, these layers spread heat dissipated by the LT83201.

Placing additional vias can reduce thermal resistance further. The maximum load current should be derated as the

ambient temperature approaches the maximum junction rating. Power dissipation within the LT83201 can be

estimated by calculating the total power loss from an efficiency measurement and subtracting the inductor loss. The

die temperature is calculated by multiplying the LT83201 power dissipation by the thermal resistance from junction

to ambient.

The internal overtemperature protection monitors the junction temperature of the LT83201. If the junction

temperature reaches approximately 165°C, the LT83201 stops switching and indicates a fault condition until the

temperature drops about 5°C cooler.

Temperature rise of the LT83201 is at its worst when operating at high load, high VIN, and high switching frequency.

If the case temperature is too high for a given application, then either VIN, switching frequency, or load current can

be decreased to reduce the temperature to an appropriate level. Figure 60 shows examples of how case temperature

rise can be managed by reducing load.

The LT83201’s top switch current limit decreases with higher duty cycle operation for slope compensation. This also

limits the output current the LT83201 can deliver for a given application. See curve in Typical Performance

Characteristics.

Figure 60. LT83201 Case Temperature Rise

DEMO BOARD, ON STILL AIR

VOUT = 3.3V

fSW = 2MHz

ILOAD = 0.5A

ILOAD = 1A

INPUT VOLTAGE (V)

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